Heretofore, as tape or disk magnetic recording media for use in audio, video, computer, etc., equipment, use has been made of magnetic recording media which has been prepared by coating on a non-magnetic support a magnetic layer comprising a ferromagnetic powder such as gamma-Fe.sub.2 O.sub.3, Co-containing iron oxide, chromium dioxide, ferromagnetic alloy powder, etc., dispersed in a binder. Recently, with such magnetic recording media becoming higher and higher in its density and S/N ratio, there has developed a practice of comminuting the magnetic material, but as this comminution inevitably reduces the abrasiveness of the magnetic material, the magnetic recording media using such a magnetic material deteriorates in running durability. The tendency is more remarkable in use of a ferromagnetic alloy powder having a low hardness.
As a contermeasure for preventing such deterioration in running durability, it has hitherto been proposed to add to the magnetic layer an abrasive such as granular Al.sub.2 O.sub.3, SiC, Cr.sub.2 O.sub.3, etc., as described, for example, in U.S. Pat. No. 4,285,825. When such an abrasive is added in a large amount, however, the magnetic recording medium has defects in magnetic orientation as well as in packing degree and dispersibility of the magnetic powder, and in turn deterioration of the surface property. As a result, electromagnetic properties degrade due to the deterioration of the surface property.
Although the electromagnetic properties can be improved if the amount of the abrasive added is reduced so as not to deteriorate the surface property, increase found in friction coefficient of the magnetic layer causes sticking during running, and thus problems arise in that running property of the magnetic recording medium is damaged.
One of the present inventors with another previously found that the above-described defects can be eliminated by a method wherein, as the abrasive, use is made of an acicular inorganic material which is not more than 1.0 micron (.mu.m) in length (the length of the long-axis thereof) and not more than 0.1 micron in width (the length of the short-axis thereof), having an acicular ratio of from 5/1 to 20/1 and a Moh's hardness of 5 or higher, as described in Japanese patent application No. 62938/85 corresponding to U.S. Pat. Ser. No. 843,973 filed Mar. 25, 1986.